I can't type anything!
First, make sure you've created a project.
Next, add one or more chapters.
After that, add a scene to the chapter.
Many people now try to enter text in the preview window at the bottom of the main screen, but there's a reason it won't work: yWriter has a built-in editor with an autobackup feature. You can open many windows at once, allowing cut & paste between them.
To open the proper editor, just double-click any scene title in the scene list, OR double-click the preview window. This will open the editor, and you can then start typing.
(On the main screen you CAN change some lesser items like Goals, Outcome, etc.)